Typical optical fibers include a core material and a cladding material, with each of the core and the cladding usually being fabricated largely from fused silica and having dissimilar refractive indices. A fiber can be formed by drawing a preform, which is a large mass that includes the core and cladding materials arranged in a shape that can resemble a cross-section of the finished fiber, but is much larger. The preform can be drawn in a fiber drawing tower during which the preform is heated and stretched from one end to form the optical fiber. The finished fiber can have a length that can be constrained by a variety of factors, including physical and operational factors such as those resulting from Raman gain and/or pump power.
The core material of a typical optical fiber can exhibit optical gain through a phenomenon called stimulated Raman scattering (SRS) according to which optical signals are amplified as they propagate through the fiber. Amplification of optical signals via SRS is dependent on both a Raman gain coefficient of the core material and the length of the optical fiber. To achieve desired Raman gain coefficients, optical fiber cores are typically doped with additional materials to increase the optical gain of the fiber. However, such doping has limitations in contributing to a Raman gain coefficient. As a result, to achieve substantial amounts of optical amplification of a given optical signal, some optical fibers have to be fabricated at a length of hundreds of meters or more. Accordingly, some optical systems require a substantial amount of physical space and/or power to maximize optical signal intensity that is provided from an optical pump or laser.